How fast is Earth moving through space? That depends.
We are hurtling through space. But where are we going?
Dr. Michelle Thaller is an astronomer who studies binary stars and the life cycles of stars. She is Assistant Director of Science Communication at NASA. She went to college at Harvard University, completed a post-doctoral research fellowship at the California Institute of Technology (Caltech) in Pasadena, Calif. then started working for the Jet Propulsion Laboratory's (JPL) Spitzer Space Telescope. After a hugely successful mission, she moved on to NASA's Goddard Space Flight Center (GSFC), in the Washington D.C. area. In her off-hours often puts on about 30lbs of Elizabethan garb and performs intricate Renaissance dances. For more information, visit NASA.
MICHELLE THALLER: Eugene, you've asked one of my favorite questions and a surprisingly deep one. The essence of it is: How fast are we really moving? We are a solar system; we are planets going around the Sun. But the Sun has its own motion around the galaxy, the Milky Way. And there are larger motions still because the Milky Way galaxy is also moving through space. So I'm going to try to break this down because there are a number of different ways to think about motion because when you get to these scales, one of the most important questions you have to ask is: Motion compared to what? And I'll explain that as I go along.
So one of the most easy to understand motions, but a kind of mind-blowing one is that the Sun is orbiting around the center of the Milky Way galaxy. Now, the Milky Way galaxy is a huge collection of about half a trillion stars, and it's about 100,000 light years across end-to-end. Now, we actually orbit around the center of the galaxy -- the center of the galaxy is about 30,000 light years away from us -- and we orbit around about once every 230 million years. OK, that sounds like a long time. So 230 million years to make one orbit around the galaxy. So how fast are we going? It turns out that the Sun, and us with it, it's going at about 560,000 miles an hour. That's over half a million miles an hour just around the center of our galaxy. So right now, you are moving at over half a million miles an hour around the center of the galaxy. And if you want to think about it in kind of a dramatic way, the center of the galaxy has a massive black hole at the middle, and it's about 4 million times the mass of the Sun. So right now, you are orbiting a massive black hole at half a million miles an hour. That's kind of fun.
But there are larger velocities as well. And here's where things start to get a little bit complicated because the universe is expanding. And what that really means is that space itself is expanding. It's not really correct to say the galaxies are flying through the universe with the expansion of the universe. That's actually not how it works at all. The galaxies in that sense are standing still, but the space in between them is getting bigger. It's a very strange thing to think about, but the expansion of the universe is not galaxies moving through empty space. And one of the reasons that this is important is because the farther away you look into space, the more expanding space you look through. And it's not that galaxies very far away are actually moving through space very, very fast, but they appear that way to us. There's something called the Hubble Constant, and what that means is how fast the universe is expanding for every amount of space that you look through. The Hubble constant right now is about 75 kilometers per second per megaparsec, and a megaparsec is about 3 million light years. So that means that every 3 million light years you go out, things are receding from you at an additional 75 kilometers per second. So when you're 3 million light years away, a galaxy would naturally recede away from you at 75 kilometers per second. Now double that. Say that you're now 6 million light years away, double 75: 150 kilometers per second. So for every 3 million light years you go out, you put an additional 75 kilometers per second onto the speed.
Now, that means the galaxies nearer to us are not moving very quickly at all in the natural expansion of the universe. But if you look at something billions of light years away, you're looking through that much expanding space, and it can be receding away from us, appearing to recede away from us, at a very fast velocity indeed. In fact, when you actually look at the very, very edges of the universe, things are receding away from us close to the speed of light. So that's not anything moving at the speed of light. That's just the fact that you're looking through that much expanding space that it appears to be going that fast away from you, and this is called the Hubble Law.
It took a long time for people to realize that there might be other motions besides just this expansion of the universe. And we have to tease them out because galaxies, as big as they are and as fast as they're moving, the distances they're moving across are so vast it's very difficult to detect. Over time we realized that yes indeed there were other motions besides this, what we call Hubble flow, this expansion of the universe. So we began to realize that the Milky Way galaxy was part of larger clusters of galaxies. And in some cases, clusters of galaxies were bound together by gravity, sort of orbiting around big groups of galaxies. And in other cases, these concentrations of galaxies are probably going to disperse over time as the universe expands.
So starting from relatively close to us, the closest large galaxy to us is Andromeda. And Andromeda is so big and so close that in fact, we are falling towards each other faster than the universe expanding us away. Right now the Andromeda galaxy is coming at us at a speed of about 300,000 miles an hour. And that means that's going to collide with us in a couple billion years so I wouldn't worry about that, that's not a problem for us at all. And in fact, we think the Milky Way has collided with other galaxies in the past as well. But the reason Andromeda is coming toward us is the force of gravity is accelerating us together faster than the expansion is taking it away. Other galaxies even closer to us are orbiting the Milky Way, like the Magellanic Clouds.
So now, let's go out a little bit further and think about how the Milky Way is moving through space compared to larger things. Well, the largest motion we know of right now is that we are falling in towards something called the Great Attractor. And this is a concentration of mass, a giant cluster of galaxies. And right now, we're moving at a little over one and a half million miles an hour towards that part of the sky. For a long time, we really didn't know what was there. We called it the Great Attractor because it seemed kind of mysterious. But now, we realize that it's actually the center of gravity of a huge cluster of galaxies, something called a super cluster. And this cluster probably contains over 100,000 galaxies, and it's probably on the order of about half a billion light years across. And this has been discovered only in the last few years, and it's been called the Laniakea Supercluster. Laniakea is the Hawaiian language word for the highest heaven. And this is the largest group of galaxies that we think that we are actually gravitationally associated with. We are actually falling in towards the center of this giant collection of galaxies.
So where's the Sun going? How are we moving? It depends on with respect to what. We're moving around the galaxy at half a million miles an hour. We're falling into the center of a supercluster of galaxies at one and a half million miles an hour. And all of that is superimposed on top of the expansion of the universe, which isn't really a speed, it's just that you have to look through a lot of expanding space. So there's no one answer as to how fast you're moving right now. And I think that's one of the most wonderful things is how complex these simple answers can get.
- How fast are you, planet Earth, our solar system, and the galaxy moving right now? There's no one answer to that question because we're going in several directions and multiple speeds all at the same time. How is that possible?
- Within the Milky Way galaxy, our solar system is orbiting around a massive black hole at the center of galaxy at half a million miles an hour. Separately, the Milky Way galaxy is in the Virgo Supercluster, which is falling into the Great Attractor, a huge group of galaxies called the Laniakea Supercluster, at one and a half million miles an hour.
- And all of that is superimposed on top of the natural expansion of the universe, which isn't really a speed, but is happening at 75 kilometers per second per megaparsec.
- 4 Things That Currently Break the Speed of Light Barrier - Big Think ›
- Six solar system oddities and why we learn about them - Big Think ›
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Research suggests that aging affects a brain circuit critical for learning and decision-making.
As people age, they often lose their motivation to learn new things or engage in everyday activities. In a study of mice, MIT neuroscientists have now identified a brain circuit that is critical for maintaining this kind of motivation.
Researchers find a key clue to the evolution of bony fish and tetrapods.
- A new study says solar and lunar tide impacts led to the evolution of bony fish and tetrapods.
- The scientists show that tides created tidal pools, stranding fish and forcing them to get out of the water.
- The researchers ran computer simulations to get their results.
Neil deGrasse Tyson Explains the Tides<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="9913a65f847775722d7c23d40d78938b"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/dBwNadry-TU?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
A study finds 1.8 billion trees and shrubs in the Sahara desert.
- AI analysis of satellite images sees trees and shrubs where human eyes can't.
- At the western edge of the Sahara is more significant vegetation than previously suspected.
- Machine learning trained to recognize trees completed the detailed study in hours.
Why this matters<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDU2MDQ1OC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzOTkyODg5NX0.O3S2DRTyAxh-JZqxGKj9KkC6ndZAloEh4hKhpcyeFDQ/img.jpg?width=980" id="3770d" class="rm-shortcode" data-rm-shortcode-id="3c27b79d4c0600fb6ebb82e650cabec0" data-rm-shortcode-name="rebelmouse-image" />
Area in which trees were located
Credit: University of Copenhagen<p>As important as trees are in fighting climate change, scientists need to know what trees there are, and where, and the study's finding represents a significant addition to the global tree inventory.</p><p>The vegetation Brandt and his colleagues have identified is in the Western Sahara, a region of about 1.3 million square kilometers that includes the desert, <a href="https://en.wikipedia.org/wiki/Sahel" target="_blank">the Sahel</a>, and the <a href="https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/subhumid-zones" target="_blank" rel="noopener noreferrer">sub-humid zones</a> of West Africa.</p><p>These trees and shrubs have been left out of previous tabulations of carbon-processing worldwide forests. Says Brandt, "Trees outside of forested areas are usually not included in climate models, and we know very little about their carbon stocks. They are basically a white spot on maps and an unknown component in the global carbon cycle."</p><p>In addition to being valuable climate-change information, the research can help facilitate strategic development of the region in which the vegetation grows due to a greater understanding of local ecosystems.</p>
Trained for trees<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDU2MDQ3MC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzNTk5NTI3NH0.fR-n1I2DHBIRPLvXv4g0PVM8ciZwSLWorBUUw2wc-Vk/img.jpg?width=980" id="e02c0" class="rm-shortcode" data-rm-shortcode-id="79955b13661dca8b6e19007935129af1" data-rm-shortcode-name="rebelmouse-image" />
Credit: Martin Brandt/University of Copenhagen<p>There's been an assumption that there's hardly enough vegetation outside of forested areas to be worth counting in areas such as this one. As a result the study represents the first time a significant number of trees — likely in the hundreds of millions when shrubs are subtracted from the overall figure — have been catalogued in the drylands region.</p><p>Members of the university's Department of Computer Science trained a machine-learning module to recognize trees by feeding it thousands of pictures of them. This training left the AI be capable of spotting trees in the tiny details of satellite images supplied by NASA. The task took the AI just hours — it would take a human years to perform an equivalent analysis.</p><p>"This technology has enormous potential when it comes to documenting changes on a global scale and ultimately, in contributing towards global climate goals," says co-author Christian Igel. "It is a motivation for us to develop this type of beneficial artificial intelligence."</p><p>"Indeed," says Brandt says, "I think it marks the beginning of a new scientific era."</p>
Looking ahead and beyond<p>The researchers hope to further refine their AI to provide a more detailed accounting of the trees it identifies in satellite photos.</p><p>The study's senior author, Rasmus Fensholt, says, "we are also interested in using satellites to determine tree species, as tree types are significant in relation to their value to local populations who use wood resources as part of their livelihoods. Trees and their fruit are consumed by both livestock and humans, and when preserved in the fields, trees have a positive effect on crop yields because they improve the balance of water and nutrients."</p><p>Ahead is an expansion of the team's tree hunt to a larger area of Africa, with the long-term goal being the creation of a more comprehensive and accurate global database of trees that grow beyond the boundaries of forests.</p>
Most people believe themselves to be less at risk from COVID-19 than others similar to them, according to a recent UCL survey conducted in the U.S.
- A study surveying 1,145 people in the U.S. found that the majority of people believed that they were less likely to catch the virus than the average person, regardless of the person's age or gender.
- The most effective way to counter the damaging effects of cognitive bias in the context of COVID-19 may be by calling on empathy in individuals.
- The dangerous effects of optimism bias may be compounded by confirmation bias, salience bias, and internet echo chambers.
Optimism bias<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDU5OTg2OS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYzMTAzNDM0Mn0.vRtlUDOpCnC_ZOdjxZUpRL5J9fnBeITmXXIPOMXOzhg/img.jpg?width=1245&coordinates=0%2C2291%2C0%2C1908&height=700" id="abbcf" class="rm-shortcode" data-rm-shortcode-id="ff0569ffedf799d7a1237068dc1ee72f" data-rm-shortcode-name="rebelmouse-image" alt="smiley paint on gray ground in front of people" />Photo by Nathan Dumlao on Unsplash<p>Most people have a tendency to overestimate the chances of experiencing a positive (like getting a promotion), and underestimate the likelihood of experiencing a negative event (like getting robbed or sick). Typically a benign — even beneficial — human quirk, the "optimism bias" could be contributing to the spread of coronavirus according to behavioral psychologists.</p><p>Experts argue that it has caused people to discount their individual chances of contracting COVID-19, despite being aware of its risk to the rest of the population. A study that was conducted over three phases this year surveying 1,145 people in the U.S. found that the majority of people believed that they were less likely to catch the virus than the average person is, regardless of the person's age or gender. </p><p>"This is very typical of what optimism bias is," Tali Sharot, a cognitive neuroscientist at University College London and lead author of the study, <a href="https://www.cnbc.com/2020/10/22/why-optimism-bias-could-be-unhelpful-in-a-pandemic-say-psychologists.html" target="_blank" rel="noopener noreferrer">told CNBC Make It</a>. "You usually believe that your likelihood of experiencing negative events is lower than people like you, and the likelihood of you experiencing positive events is higher than other people like you."</p><p>According to Sharot, optimism bias is a product of our tendency to vividly imagine positive future events and attribute more probability to them happening. </p><p>In certain circumstances, such as in our jobs and relationships, this can be beneficial by encouraging us to behave in ways that may contribute to positive outcomes, thus becoming a self-fulfilling prophecy. But we're in a pandemic, and it's having a concerning impact on our ability to assess risk and react appropriately. As time goes on and COVID-19 cases <a href="https://www.cnn.com/2020/10/26/health/us-coronavirus-monday/index.html" target="_blank" rel="noopener noreferrer">continue to rise and spread</a> the threat of the virus is becoming a background hum to everyday life making this bias worse. </p><p>"I think now the risk is greater because we have gotten used to this threat. And when you get used to a threat you underestimate it even more," said Sharot.</p><p>The United States is now reporting the greatest number of cases it's seen to date, with a seven-day average of daily new cases reaching 68,767 on Sunday, according to data from Johns Hopkins University. </p>
Other menacing biases<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDU5OTg3Mi9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY2MzA1OTMwOX0.f68UAZY--fN5yJ_26v7OjhQG5Ieda_HQx_iDF5NKHJI/img.jpg?width=1245&coordinates=0%2C30%2C0%2C31&height=700" id="79c78" class="rm-shortcode" data-rm-shortcode-id="8b155c7f4503e53d756c1451be9874c8" data-rm-shortcode-name="rebelmouse-image" />
Credit: Michael Siluk/Education Images/Universal Images Group via Getty Images<p>Optimism bias may be compounded by <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7144592/" target="_blank">confirmation bias</a>, or the tendency to interpret new information as confirmation of one's existing beliefs or theories while disregarding information that contradicts one's preferred narrative of reality. Salience bias is also at play, leading people to underplay or discount the threat of something they cannot see such as a microscopic virus or sick people in the hospital.</p><p>Additionally, internet echo chambers exacerbate these cognitive biases. When others share our viewpoints, our biases are typically inflated, and it's never been easier to curate our social circles with networks of people who do exactly that. This feeds into the tribalism and polarization that has added to the challenges of getting a majority of the U.S. population to comply with virus safety measures. Think, for example, how the act of <a href="https://bigthink.com/coronavirus/face-masks-transmission" target="_blank">wearing a mask has become politicized</a> in the U.S. as a perceived badge as to which group one belongs to, masks often being associated with liberal-leaning people and no masks (<a href="https://bigthink.com/coronavirus/christian-nationalism" target="_blank">anti-maskers</a>) being associated with the far-right. </p>