Lawrence Krauss discusses colliding stars, missing mass and more

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Arizona State University physicist Lawrence Krauss joins Arizona Horizon to discuss the latest science news.

Krauss explains the recent sighting of light from gravitational waves produced by the collision of two neutron stars.

“The fact that we knew they were neutron stars meant we could learn so much,” Krauss said. The Oersted Medal-winning physicist believes this discovery could change the course of astronomy.

Coming up next on Arizona horizon, colliding stars, a visitor from another universe and the discovery of missing matter. We'll sort it all out with physicist Lawrence Kraus. And a discussion with 1st-amendment lawyer Floyd Abrams about what is and is not protected speech. Those stories next on Arizona horizon. Arizona "horizon" is made possible by contributions from the friends of Arizona PBS. Members of your PBS station. Thank you.
Ted Simons: Good evening and welcome to Arizona horizon. I'm Ted Simons. Republicans on Capitol Hill today released a tax plan that includes a variety of cuts, along with changes to deductions. Reaction from Arizona lawmakers was mixed. We have been hearing a lot about cuts, cuts, cuts. If we are going to do cuts, cuts, cuts, we have got to do wholesale reform. On the democratic side, congressman tom O’Halloran, who represents Arizona's 1st-congressional district, said in a statement, quote, "I am concerned that many critical deductions, on which millions of Americans rely, could be eliminated. Additionally, I worry that our corporate tax policy will not do enough to encourage businesses to bring back American jobs or create new jobs in our communities. President trump says he hopes to have the tax-reform package signed into law by the end of the year. All are some -- there are some amazing things happening in the universe: we've got stars colliding, we've got an object from outer space visiting our solar system and we've got the discovery of half of the missing matter in our universe. Here to explain it all is our resident expert on all things scientific, physicist Lawrence Kraus.
Lawrence Kraus: Good to be back to talk about the mysteries of the cosmos.
Ted Simons: We talked about this before. Let's get a better picture. Two neutron stars collide and everybody makes a big deal.
Lawrence Kraus: It is a big deal. I saw the program and it is so neat it is worth spending more time on. You have the observation of gravitational waves from these two neutron stars 130 million light-years away. Before the dinosaurs roaming around, or when they were, these two neutron stars collided and we would never have known about it without this gravitational detector that detected the most minute change. It would have been indiscernible a generation ago. But that observation set off a tidal wave because we saw that we knew it was two neutron stars colliding because only that would produce that gravitational wave signal. That meant the possibility that every other astronomer on the universe, or earth, could look out with their telescopes, x-rays, gamma rays, could all look at that object. We have two gravitational wave detector seeing it. Unlike black holes when they collide nothing comes out. With the neutron stars, it meant there could be a visible signal. Visible signals which we might have seen by accident but wouldn't have known what they were. The fact we knew they were neutron stars we could learn so much. The first thing you see, I don't know if you can run the video, but the first thing you see when those neutron stars collide, there are two objects, the mass and sun, orbiting each other a thousand times a second, and boom at the last moment, they produce the gravitational waves. All the stuff comes out. The first thing is an amazing jet of material propelled by the magnetic field. That jet produces gamma rays. We will come back to the video. It is going to show this. The first thing you see as a jet is energy getting gamma way -- rays --. Two seconds later you see the gravitational waves. Already we have learned something. It is 130 million light years away. The gravitational waves are generated before the two objects hit. The two objects hit, the gamma rays come out and we predict a second. They were observed within two seconds apart meaning gravitational and light waves traveled the same speed. Over 130 million years they arrive within a second of each other. That proves something we would never have proved otherwise and that is light and gravity travel at the same speed to one part in a million billion.
Ted Simons: I am imaging this happens with frequency. Will we be able to see it again?
Lawrence Kraus: We expect it happens in a way that is detectable by these detectors once a week.
Ted Simons: Once a week?
Lawrence Kraus: In the universe, it is happening every second but the detectors can only detect neutron star collisions to maybe a billion light years but that is enough to once a week. The gravitational waves and then the boom as they merge. Then you see the jets and this big cloud in the center. That stuff is being ejected from these neutron stars. That stuff is the outer parts of the stars, rich in neutrons, which are interacting with the background gas outside the neutron stars which contains atoms and dumping neutrons in the atoms and the nuclei. We never knew, well we assumed this might be what happens, because you see in stars, the only materials that are made are everything up to iron. Everything past iron has a lot more neutrons than protons. We wondered where that process can be that would dump neutrons so fast and we thought one way is neutron slides colliding and there is so many dense neutrons. The stars, I remind you, the mass of the sun the size of Manhattan. A teaspoon of material weighs more than Mount Everest. It is amazing. They are dense. They are basically two giant nuclei that collide and the stuff coming out is rich in neutrons and interacts with the atoms and produces all the rings. Is your wedding ring gold?
Ted Simons: Yes.
Lawrence Kraus: Know where it came from?
Ted Simons: Two neutron stars.
Lawrence Kraus:: Exactly. It is at the speed of light and it will go out and permeate the galaxally it is in. There may be beings in the galaxy having a conversation on to about the gold. But if they were near the explosion they would not be having the conversation.
Ted Simons: Somewhere in the galaxy, we saw all this stuff coming out of the middle there. That’s 130 million years ago. So how far does that stuff go before it dissipates?
Lawrence Kraus: Well it’s speeding out at almost at the speed of light. It’s going to go out and permeate the galaxy that it’s in. It’s going to sprinkle and seed gold. There may be beings in that galaxy that are having a conversation of television right now about the gold. Except if they were near that explosion they wouldn’t be having that conversation.
Ted Simons: A couple neutron stars at some time in the past probably had a similar situation and thus my gold ring.
Lawrence Kraus: Exactly. It is happening all the time. We could measure it by looking at the visible light because the visible light comes from when the heavy atoms are formed and the neutrons cascade down. We could estimate 100 earth masses of gold were produced in that ring. Isn't that amazing?
Ted Simons: it is.
Lawrence Kraus: Maybe every week we can talk about it. We only have about five minutes left. We have an interstellar object. This from who knows where comes flying in.
Lawrence Kraus: This is a visitor from outside the solar system. Two young people are looking at using a telescope in Hawaii were able to -- you take pictures of the sky at night and we do this looking for asteroids that might collide with the earth. We take the same picture each night and see if there is an object moving and what they discovered was an object moving like no one has seen before. I think we have a video. Coming in out of nowhere into our solar system. Here is this object coming down from above and deflects from the sun and passes 15 million miles near the earth. 60 times the distance from the moon. It is travelling faster than anything that would be observed in our solar system. A trajectory that can't be part of the solar system. It is a visitor from somewhere else in the galaxy.
Ted Simons: It gets moved around and shoots on out.
Lawrence Kraus: We predicted. When planets are formed and objects get ejected we predicted there would be visitors from the outer solar system and elsewhere in the universe. What is interesting is that has been happening. Many questions you might have, maybe life was seated by a material elsewhere in the galaxy. We have seen the first objects that demonstrate we know those items are coming.
Ted Simons: What if it hit the earth? Or the sun? If it hits the sun, it just goes into the sun and -- the sun swallows it?
Lawrence Kraus: Yes. It does that all the time. Hits the earth, bad news.
Ted Simons: Was this a comet or asteroid?
Lawrence Kraus: We don't know. We know it was 400 meters in India -- in diameter which could was damage but not wipe out the earth. It would deposit its materials on earth and we know that in asteroids and comets there are complex molecules. And some people argue actually the major ingredients of complex organic molecules may be from a past civilization that destroyed each other may have come from an asteroid.
Ted Simons: something happened then.
Lawrence Kraus: Yeah, something happened to destroy the planet and those objects may survive in an asteroid or comet. Such objects have hit the earth in the past. No one had ever seen a visitor from outer space. Thought was the first visitor.
Ted Simons: You touched on this a second. Could it be possible in a non-science fiction novel that some sort of bacteria, or something from a civilization long ago and far away, comes zooming in and hits the earth and here we are.
Lawrence Kraus: We could be aliens from a different sell solar system. You have been able to survive. Not likely bacteria but maybe the basis of rna. But one of the people that discovered dna used this term saying maybe life doesn't evolve but the reason it evolved so easy because it came from out there.
Ted Simons: Will we discover more now that we have this one?
Lawrence Kraus: Probably. We have eyes on the system because we are worried about asteroids that might hit the earth. We have objects looking in the sky every night.
Ted Simons: because of your excitement, we can't get to the third one. Missing matter. It is still missing.
Ted Simons: Good to see you.
Lawrence Kraus: You take care.
Ted Simons: Coming up, a discussion with noted 1st-amendment attorney Floyd Abrams about free speech on college campuses. That's next on Arizona horizon.

Lawrence Krauss: Physicist, Arizona State University

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