Hello everyone!
This week on The Cosmic Companion, we take on a weighty subject — gravity. Later in the show, we are going to talk with Joe Swiggum from the NanoGrav Collaboration.
Gravity is one of those things that we all know about, but when you really stop to think about it, it’s pretty mind-boggling. I mean, there’s this invisible force that keeps us all stuck to the ground and makes things fall when we drop them. How wild is that?
Joe Swiggum appears on The Cosmic Companion 19 August 2023. Creative Commons 4.0 2023 The Cosmic Companion.
Our understanding of gravity has changed a lot over time. The ancient Greeks had some ideas about it — Aristotle thought that earth and water fell towards the Earth while fire and air rose as each of the ancient “elements” traveled toward their natural position.
Isaac Newton came along in the 17th century, giving us a real handle on what gravity is all about. Newton realized that gravity is a force causing any two bodies to be attracted towards each other. The strength with which they do this depends on their masses and the distance between the bodies.
Incidentally — although Newton might have seen an apple drop onto the ground while thinking about gravity, the story about Newton being bopped in the head is probably not true. That type of thing just doesn’t happen.
The story of the falling apple first appeared in print in a biography written by William Stukeley, who was a friend of Newton.
Although Stukeley recounted that Newton had told him about the event during a conversation, his biography of Newton wasn’t published until 1752, more than 50 years after the alleged incident.
Later, it turned out that Newton’s ideas weren’t the whole story. In 1916, Albert Einstein proposed a new theory of gravity called general relativity. According to his ideas, gravity might be thought of as a curvature of spacetime resulting from the presence of mass.
General relativity predicts that light should be affected by gravity, even though light doesn’t have any rest mass. And sure enough, experiments have confirmed that light does indeed bend when it passes near a massive object like a star or galaxy.
Gravitational waves — ripples in the fabric of spacetime — have been seen emanating from the movement of massive objects in space. This advance provides researchers with a new branch of science — gravitational astronomy.
However, smaller constant ripples of gravitational waves passing through spacetime are also predicted by the theories of physics. Such tiny gravitational background ripples were recently detected for the first time by researchers at the NanoGrav Collaboration.
Next up, we talk with Joe Swiggum from the NanoGrav Collaboration, talking about this exciting observation.
We’ve come a long way in our understanding of gravity, but there are still plenty of questions that researchers are trying to answer. For example, one big mystery is why gravity is so much weaker than the other fundamental forces of nature.
I mean, think about it — you can pick up a paperclip with a tiny magnet, even though the entire Earth is pulling on that paperclip with its gravity.
What’s that you say? You want to prove that with an experiment? Fine. Follow me into the laboratory…
Another big question has to do with how gravity fits in with quantum mechanics, which is our best theory for describing the behavior of particles on very small scales.
Right now, we don’t know of a good way to combine general relativity and quantum mechanics into a single theory — this is sometimes called the problem of “quantum gravity”. This is one of the great questions in cosmology today.
So there you have it — gravity is one of those things that seems simple at first glance but turns out to be full of surprises. What would life be like without gravity?
G.R. Avity is in da house!
In a world without gravity, we’d all be floating free. No more falling down, no more scraped knees!
We’d be bouncing off walls, doing flips in the air. No more heavy lifting, no more squeaky chairs!
We’d be soaring right through space, weightless and free. No more limits, no more boundaries!
We’d be flying over town, with nothing to hold us down. In a world without gravity, we’d all wear the crown!
But without gravity, there’d be no more mic drop. So let’s keep it real and never ever ever stop!
We won’t have a show next week, as we continue work on our first feature-length film, Gaia Rising.
This future history explores a 21st century facing devastation from global climate change, telling the story of three disparate individuals who come together to heal our wounded planet.
This first trailer for Gaia Rising will be released (right here!) on 2 September. Make sure you join us then!
Clear skies!
James
P.S. On 16 September, we will be looking at Artificial Intelligence and the Future of the Human Race. We will have an EXTRA-SPECIAL SPECIAL GUEST that day!
We will announce our guest for that episode on Wednesday, 30 August — but our VIP subscribers will be the first to know and will get a special sneak preview of our upcoming episode on Saturday, 26 August - four days before everyone else. Wow! (This is TOTALLY going to be awesome!)
Subscribe already, why don’t ya?
Gravity - a Weighty Subject! with Joe Swiggum, NanoGrav Collaboration