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Ask an astronomer! Should we block out the sun to stop climate change?

Michelle Thaller from NASA examines if it's possible to put up a giant disk to block out the sun's rays and cool Earth.

Lisa, I share your concern about climate change. This is something that’s one of the biggest challenges that humanity has ever faced, and it’s something that in the next couple of decades and centuries we’re going to have to really band together and work together to solve.

And when you ask a question like you did, about “how might you solve climate change,” it actually gives me a lot of hope because it means that young people like you are really starting to think about ideas about how we could address climate change.

You said, “could you build a giant disk and put it between the earth and the sun and have it act as a kind of sunshade actually cooling down the earth?” That’s a wonderful idea. There are some things about that that would be quite difficult and one thing is that the sun is actually very large, it’s much larger than the earth, so it actually projects light around anything that you put up there.

You’d have to put a very, very large disk up there. It might have to be something roughly the size of the planet in order to shade the planet effectively against the sun. So that’s something that might be possible, but it would be very expensive and difficult to construct. But I love the fact that you’re thinking about it.

It does however to me sort of not address the underlying problems with climate change. A lot of people have ideas similar to yours that, what if we could just block out some of the sun’s light, would that actually make climate change go away? And one of the ideas people have is possibly launching lots and lots of particles of dust up into the atmosphere.

We observed that when there’s a volcanic explosion and the earth naturally puts lots and lots of dust up into the atmosphere, the earth’s climate cools. We observed this in the ‘90s when Mount Pinatubo erupted and we actually had a decline, a little bit of a notch on the global warming, just due to this volcano putting lots and lots of stuff up into the atmosphere.

So could we do that artificially could we just darken our atmosphere to actually have less sunlight get through? The answer is yes, we probably could, but it would be a huge effort.

A single volcano puts up many, many thousands of tons of dust up there, so this would have to be something continuous: lots and lots of rockets or aircraft distributing dust across the atmosphere. And the thing that kind of frightens me is that we really don't understand our atmosphere enough to know what that sort of cooling would do. The atmosphere stores heat, it creates winds and of course the air moves around, there are storms; scientists spend a lot of time studying how the atmosphere stores heat, how the weather forms, and when you darken the atmosphere I’m not sure what it would do to our weather. It would be a very dangerous experiment to do if you couldn’t control it.

And the same thing with building a disk: I’m not sure that darkening the earth is a very good idea; it may change things like weather patterns or even ocean currents, the winds, all of that. It also doesn’t get at the problem of carbon dioxide.

Now the reason our atmosphere is getting warmer and warmer and warmer is because we humans are putting lots of carbon dioxide up into the atmosphere and this acts as what we call a greenhouse gas. Sunlight can get through the atmosphere but the carbon dioxide traps it and it can’t release itself back into space so it gets warmer and warmer over time. Carbon dioxide doesn’t just warm the atmosphere, it also affects our oceans. When ocean water combines with carbon dioxide it creates something called carbonic acid and it makes the oceans more and more acidic over time and this is a really big problem for marine life. There are things like algae, the algae in the oceans are responsible for most of the oxygen that we breathe, and the algae are having trouble forming because of the higher acid levels in the ocean.

So even if the one thing you solved was cooling the earth down, if we continue to put more and more carbon dioxide into our atmosphere there will be other serious repercussions. We could end up killing the ocean life system, for example.

So the problem really isn’t an external one, it’s not simply cooling the planet putting up lots of dust or building a wonderful shade like you suggest, the problem is really getting at our emissions of carbon dioxide and stopping those and stopping these dramatic changes that we see coming. Some of them are going to be very difficult to stop. I mean right now we’re observing the ice caps at both poles of the planet, in Antarctica and in the North Pole, melting very quickly. That won’t stop. Those ice caps will largely melt over many, many centuries and the ocean levels will rise in accordance.

I do think right now the challenge is how are we going to deal with the changes? We might not be able to change very many of them at this point, we need to band together as people make sure that we have ways to deal with refugees—people need to leave where they are because the oceans are rising. There’s going to be a lot of people that need homes, and there’s going to be a lot of support needed for the changes in agriculture, in fishing, in so many parts of our economy and our lives. There’s no easy solution. I do love that you’re thinking about it, and we need you to keep doing that.

Couldn't we just put up a giant disk to block out the sun's rays and cool Earth? Michelle Thaller from NASA answers if that's possible. She also wonders if any such solution is really looking at the underlying causes of climate change.

A new hydrogel might be strong enough for knee replacements

Duke University researchers might have solved a half-century old problem.

Photo by Alexander Hassenstein/Getty Images
Technology & Innovation
  • Duke University researchers created a hydrogel that appears to be as strong and flexible as human cartilage.
  • The blend of three polymers provides enough flexibility and durability to mimic the knee.
  • The next step is to test this hydrogel in sheep; human use can take at least three years.
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Predicting PTSD symptoms becomes possible with a new test

An algorithm may allow doctors to assess PTSD candidates for early intervention after traumatic ER visits.

Image source: camillo jimenez/Unsplash
Technology & Innovation
  • 10-15% of people visiting emergency rooms eventually develop symptoms of long-lasting PTSD.
  • Early treatment is available but there's been no way to tell who needs it.
  • Using clinical data already being collected, machine learning can identify who's at risk.

The psychological scars a traumatic experience can leave behind may have a more profound effect on a person than the original traumatic experience. Long after an acute emergency is resolved, victims of post-traumatic stress disorder (PTSD) continue to suffer its consequences.

In the U.S. some 30 million patients are annually treated in emergency departments (EDs) for a range of traumatic injuries. Add to that urgent admissions to the ED with the onset of COVID-19 symptoms. Health experts predict that some 10 percent to 15 percent of these people will develop long-lasting PTSD within a year of the initial incident. While there are interventions that can help individuals avoid PTSD, there's been no reliable way to identify those most likely to need it.

That may now have changed. A multi-disciplinary team of researchers has developed a method for predicting who is most likely to develop PTSD after a traumatic emergency-room experience. Their study is published in the journal Nature Medicine.

70 data points and machine learning

nurse wrapping patient's arm

Image source: Creators Collective/Unsplash

Study lead author Katharina Schultebraucks of Columbia University's Department Vagelos College of Physicians and Surgeons says:

"For many trauma patients, the ED visit is often their sole contact with the health care system. The time immediately after a traumatic injury is a critical window for identifying people at risk for PTSD and arranging appropriate follow-up treatment. The earlier we can treat those at risk, the better the likely outcomes."

The new PTSD test uses machine learning and 70 clinical data points plus a clinical stress-level assessment to develop a PTSD score for an individual that identifies their risk of acquiring the condition.

Among the 70 data points are stress hormone levels, inflammatory signals, high blood pressure, and an anxiety-level assessment. Says Schultebraucks, "We selected measures that are routinely collected in the ED and logged in the electronic medical record, plus answers to a few short questions about the psychological stress response. The idea was to create a tool that would be universally available and would add little burden to ED personnel."

Researchers used data from adult trauma survivors in Atlanta, Georgia (377 individuals) and New York City (221 individuals) to test their system.

Of this cohort, 90 percent of those predicted to be at high risk developed long-lasting PTSD symptoms within a year of the initial traumatic event — just 5 percent of people who never developed PTSD symptoms had been erroneously identified as being at risk.

On the other side of the coin, 29 percent of individuals were 'false negatives," tagged by the algorithm as not being at risk of PTSD, but then developing symptoms.

Going forward

person leaning their head on another's shoulder

Image source: Külli Kittus/Unsplash

Schultebraucks looks forward to more testing as the researchers continue to refine their algorithm and to instill confidence in the approach among ED clinicians: "Because previous models for predicting PTSD risk have not been validated in independent samples like our model, they haven't been adopted in clinical practice." She expects that, "Testing and validation of our model in larger samples will be necessary for the algorithm to be ready-to-use in the general population."

"Currently only 7% of level-1 trauma centers routinely screen for PTSD," notes Schultebraucks. "We hope that the algorithm will provide ED clinicians with a rapid, automatic readout that they could use for discharge planning and the prevention of PTSD." She envisions the algorithm being implemented in the future as a feature of electronic medical records.

The researchers also plan to test their algorithm at predicting PTSD in people whose traumatic experiences come in the form of health events such as heart attacks and strokes, as opposed to visits to the emergency department.

Hints of the 4th dimension have been detected by physicists

What would it be like to experience the 4th dimension?

Two different experiments show hints of a 4th spatial dimension. Credit: Zilberberg Group / ETH Zürich
Technology & Innovation

Physicists have understood at least theoretically, that there may be higher dimensions, besides our normal three. The first clue came in 1905 when Einstein developed his theory of special relativity. Of course, by dimensions we’re talking about length, width, and height. Generally speaking, when we talk about a fourth dimension, it’s considered space-time. But here, physicists mean a spatial dimension beyond the normal three, not a parallel universe, as such dimensions are mistaken for in popular sci-fi shows.

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How often do vaccine trials hit paydirt?

Vaccines find more success in development than any other kind of drug, but have been relatively neglected in recent decades.

Pedro Vilela/Getty Images
Surprising Science

Vaccines are more likely to get through clinical trials than any other type of drug — but have been given relatively little pharmaceutical industry support during the last two decades, according to a new study by MIT scholars.

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