Hello, scientists!
First of all, I must apologize for not posting an entry recently. I went to a place without Internet and haven't had the time to make one.
From the title, you may think that the galaxies we will talk about has an ill fate, and that may be true. However, read on, and you may find that I may be speaking literally.
First of all, I should introduce these two galaxies. One is the Milky Way, our galaxy, and the other is Andromeda, a close neighbor of ours. The Milky Way contains about 300 billion stars, and Andromeda contains about 1 trillion. Remember that, it will later fascinate you about how large galaxies are (if that didn't convince you already).
It's now time to look at an optical illusion of sorts. Have you noticed that if a siren approaches you, its pitch increases, and when it moves away, it gets lower? This is called the Doppler Effect, when sound waves either compress or stretch relative to an observer. Basically, waves get shorter as they get closer, and get longer as they get farther away.
I did say that this was an optical illusion, not an auditory one. This is because this doesn't affect just sound waves; it affects light waves as well. If you look at a poster, you'll see that red wavelengths are longer than blue ones. This means that if an object moves away from you or towards you very quickly, it will turn slightly red or blue, respectively. You'll probably never use this unless you're an astronomer or physicist, but it still happens.
You can notice this when looking through a very powerful telescope. Because the universe is expanding, all galaxies are moving away from us. Because this is on a galactic scale, though, they are moving incredibly quickly. This causes them to appear red. This is called red shift. Scientists often have to alter a picture of a galaxy because of this effect.
In that last paragraph, I lied to you. Not all galaxies are moving away from us. One notable exception is, as you may have guessed, Andromeda. When viewed, it does not produce red shift, but instead blue shift, meaning that is moving towards us. Scientists now predict that these galaxies will collide. Uh-oh.
We shouldn't worry, though. For one reason, the collision will happen about 4 billion years in the future. Also, the likelihood of a stellar collision is unbelievably small. This is because the closest distance between stars in our galaxy is like two ping-pong balls two miles away from each other. This means that all stars will most likely pass by each other without a problem.
Where's the proof? Well, there isn't any, there's no way to predict every star's exact birth, death, and path (or if there is, we probably couldn't figure it out in 4 billion years). However, another analogy may help. If the Sun was a pin-pong ball, our nearest neighbor, the star Proxima Centauri, would be a pea 680 miles away, and the Milky Way would span a fifth of the distance from the Earth to the Sun. In short, nothing is actually going to collide. Probably.
Thanks for reading! Let me know suggestions for next time, mistakes, or stuff I missed in the comments below! Tomorrow we'll discuss a physics question, so make sure to check in tomorrow.
Until next time,
Ben's jamin'
Benjamin
P.S. Make sure you check out John's math blog at http://johncooksmathblog.blogspot.com.
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