Our universe is driven by cause and effect. What happens now leads directly to what happens later. Because of this, many things in the universe are predictable. We can predict when a solar eclipse will occur, or how to launch a rocket that will take a spacecraft to Mars. This also works in reverse. By looking at events now, we can work backward to understand what happened before. We can, for example, look at the motion of galaxies today and know that the cosmos was once in the hot dense state we call the big bang.Continue reading “The three-body problem shows us why we can’t accurately calculate the past”
Astronomers have a dark energy problem. On the one hand, we’ve known for years that the universe is not just expanding, but accelerating. There seems to be a dark energy that drives cosmic expansion. On the other hand, when we measure cosmic expansion in different ways we get values that don’t quite agree. Some methods cluster around a higher value for dark energy, while other methods cluster around a lower one. On the gripping hand, something will need to give if we are to solve this mystery.Continue reading “The Chemicals That Make Up Exploding Stars Could Help Explain Away Dark Energy”
There are several ways to look for alien life on distant worlds. One is to listen for radio signals these aliens might send, such as SETI and others are doing, but another is to study the atmospheres of exoplanets to find bio-signatures of life. But what might these signatures be? And what would they appear to our telescopes?Continue reading “During A Lunar Eclipse, It’s A Chance To See Earth As An Exoplanet”
The latest observations of Betelgeuse show that the star is now beginning to slowly brighten. No supernova today! Nothing to see, better luck next time.
Despite some of the hype, this behavior is exactly what astronomers expected. Betelgeuse is a very different star from our Sun. While our Sun is a main-sequence star in its prime of life, Betelgeuse is a red giant star on the verge of death. But the death of a star is not a simple process.Continue reading “Betelgeuse Is Brightening Again”
When astronomers talk about an optical telescope, they often mention the size of its mirror. That’s because the larger your mirror, the sharper your view of the heavens can be. It’s known as resolving power, and it is due to a property of light known as diffraction. When light passes through an opening, such as the opening of the telescope, it will tend to spread out or diffract. The smaller the opening, the more the light spreads making your image more blurry. This is why larger telescopes can capture a sharper image than smaller ones.Continue reading “How Interferometry Works, and Why it’s so Powerful for Astronomy”
We can create matter from energy in the lab. Particle accelerators do this all the time. When we do, half of what is created is matter and the other half antimatter. There is a symmetry in physics that requires matter and antimatter to appear in equal amounts. But when we look around the universe, what we see is matter. So how did the big bang create all the matter we see without creating an equal amount of antimatter? The answer could be neutrinos.Continue reading “Did Neutrinos Stop The Early Universe From Annihilating Itself?”
Although neutrinos are mysterious particles, they are remarkably common. Billions of neutrinos pass through your body every second. But neutrinos rarely interact with regular matter, so detecting them is a big engineering challenge. Even when we do detect them, the results don’t always make sense. For example, we’ve recently detected neutrinos that have so much energy we have no idea how they are created.Continue reading “Neutrinos Have Been Detected With Such High Energy That The Standard Model Can’t Explain Them”
The theory of general relativity is packed with strange predictions about how space and time are affected by massive bodies. Everything from gravitational waves to the lensing of light by dark matter. But one of the oddest predictions is an effect known as frame-dragging. The effect is so subtle it was first measured just a decade ago. Now astronomers have measured the effect around a white dwarf, and it tells us how some supernovae occur.Continue reading “Astronomers See Space Twist Around A White Dwarf 12,000 Light Years Away”
Dark matter has long been one of the most mysterious things in the cosmos. It was first proposed in the 1930s as an idea to address stellar motion in some galaxies. The first solid evidence of dark matter was gathered by Vera Rubin, who studied the rotational motion of galaxies. The motion of these galaxies didn’t add up unless they contained a large amount of unseen mass. There must be some exotic, invisible matter unlike anything known before.
If dark matter exists, then it must have two major properties. First, it cannot interact strongly with light, otherwise we would see it and it wouldn’t be “dark.” Second, it must interact with other matter gravitationally, to make visible matter move in strange ways. We know of several things that satisfy those conditions, such as neutrinos or tiny black holes, but these can’t be dark matter. We know this in part because we are now able to take its temperature.Continue reading “The Debate Over Cold Dark Matter Warms Up As Astronomers Take Its Temperature”
In a recent post I wrote about a study that argued dark energy isn’t needed to explain the redshifts of distant supernovae. I also mentioned we shouldn’t rule out dark energy quite yet, because there are several independent measures of cosmic expansion that don’t require supernovae. Sure enough, a new study has measured cosmic expansion without all that mucking about with supernovae. The study confirms dark energy, but it also raises a few questions.Continue reading “There’s a new method to measure the expansion rate of the Universe, but it doesn’t resolve the Crisis in Cosmology”