Organization:365 Days Of Astronomy
Description: Space scoop, news for children.
Bio: Richard Drumm is President of the Charlottesville Astronomical Society and President of 3D – Drumm Digital Design, a video production company with clients such as Kodak, Xerox and GlaxoSmithKline Pharmaceuticals. He was an observer with the UVa Parallax Program at McCormick Observatory in 1981 & 1982. He has found that his greatest passion in life is public outreach astronomy and he pursues it at every opportunity.
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This is the 365 Days of Astronomy Podcast. Today we bring you a new episode in our Space Scoop series. This show is produced in collaboration with Universe Awareness, a program that strives to inspire every child with our wonderful cosmos.
Gravity: The Force Awakens
You’ve probably heard the phrase “what goes up must come down”, but have you ever stopped to think about why? Well, the answer, of course, is ‘gravity’.
Gravity is an invisible force that pulls objects toward each other. Anything that has mass has gravity.
OK, but what’s mass?
Mass is basically an intrinsic property of an object’s matter. But matter isn’t as well defined as we’d hope. The binding energy that holds quarks together is a significant part of what we call the rest mass of an object.
Mass can be described as the result of particles that have a rest mass coupling with the Higgs field.
While this sounds simple enough, it really, really isn’t. This is a rabbit hole that the smartest minds on Earth have gone down and haven’t yet come back up out of.
Here there be particle physics dragons!
Weight is a measure of something’s resistance to free falling in the local gravitational field.
Weight is the force that opposes free fall and is measured in newtons. A 100kg mass requires 982 newtons of force to be applied to it to keep it from free falling. This is a little bit over 220 pounds for the parts of the world that use that measure.
So the astronauts on the ISS are truly weightless because there’s nothing stopping them from being in free fall. They’re free falling all the time. But they are not massless.
A 100kg mass here on Earth is still 100kg when it’s on the ISS and 100kg on the Moon, even though it weighs 163 newtons there, or about 36.5 pounds.
Now where was I… Oh yeah!
The more mass an object has, the stronger its gravity is.
Some of the most massive things in the Universe are galaxies, enormous things containing billions of stars, planets, cosmic gas and other stuff.
Despite the huge distances between galaxies their powerful gravity is always at work. It makes them pull at each other and if the galaxies are close enough together it often leads to collisions.
We call these collisions galactic mergers. It’s a common phenomenon, happens all the time.
Consider the case of NGC 5256, a colorful but oddly shaped galaxy. Do a Google Images search for it and you’ll see.
The pair of galaxies have been crashing together for millions of years. They probably have already had one close pass and are making a second pass that distorts the two even more. Pulled together by gravity, they are slowly merging to form one larger galaxy.
Almost every galaxy will be the victim of a cosmic collision at some point. Another good example of a galactic merger, and one that you can see in a backyard telescope, is the Whirlpool Galaxy, M51, in the constellation Canes Venatici.
Google it and you’ll see the beautiful grand design spiral galaxy M51 colliding with an irregularly shaped dwarf galaxy, NGC 5195.
Hey, Here’s A Cool Fact:
Our own Galaxy has a long history of collisions with others. It contains bits of many smaller galaxies that smashed into it in the past.
You listeners in Australia & the Southern Hemisphere are likely familiar with the Magellanic Clouds. These are 2 irregular dwarf galaxies that our Milky Way is merging with and can easily be seen with the naked eye.
For the Northern Hemisphere listeners, you can look for the Andromeda Galaxy, M31. This is visible to the naked eye as well, but is dimmer than the Magellanic Clouds.
You can use an app in your smartphone to help you find it in the night sky. It’s a fine sight in binoculars. This galaxy is going to merge with the Milky Way in a few billion years.
But don’t worry, none of their stars will collide with our stars. We’ll pass right through each other like the proverbial ghost passing through a wall!
The gas between the stars in both galaxies, however, will collide. This will lead to a burst of millions of new stars being born. A cosmic Baby Boom!
End of podcast:
365 Days of Astronomy
The 365 Days of Astronomy Podcast is produced by Astronomical Society of the Pacific. Audio post-production by Richard Drumm. Bandwidth donated by libsyn.com and wizzard media. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org. This year we will celebrates the Year of Everyday Astronomers as we embrace Amateur Astronomer contributions and the importance of citizen science. Join us and share your story. Until tomorrow! Goodbye!