How do scientists measure the mass of the universe?
30 replies, posted
Ever since physicists started talking about dark matter, and how the mass of the universe is unexplainable without this dark matter, I've been totally not skeptical until 2 days ago. I thought to myself, how the fuck can physicists figure out the mass of an accelerating universe? Like what methods?
They put in on a scale.
estimation, probability, and attempted hypothesis..
[quote=pie_is_good;20060027]they put in on a scale.[/quote]
gtfo
[editline]03:58PM[/editline]
[QUOTE=BlackDeath292;20060041]estimation, probability, and attempted hypothesis..[/QUOTE]
you too
You ask a question and tell the answerers to gtfo then rate yourself agree?
I would also guess estimation but I´m no scientist
[QUOTE=TheMetalMan;20060043]gtfo
[editline]03:58PM[/editline]
you too[/QUOTE]
is this a quiz or a curious question?
cause honestly i don't know. was just my guess.
[QUOTE=swno1;20060107]You ask a question and tell the answerers to gtfo then rate yourself agree?
I would also guess estimation but I´m no scientist[/QUOTE]
You guys aren't getting the question?
How can you estimate the size of an accelerating size of a universe? Like if you stop the expansion of the universe, and send light and expect the light to reach the end of this universe it will take like a million Earth life times to reach it (if I'm not underestimating).
Like if you don't know, then don't give me a bullshit answer like hypothesis, or estimation. Tell me what's tests have they done, or what proof that they have. Give me what these physicists did to say that the universe at time = t is size = x.
[QUOTE=TheMetalMan;20060162]You guys aren't getting the question?
How can you estimate the size of an accelerating size of a universe? Like if you stop the expansion of the universe, and send light and expect the light to reach the end of this universe it will take like a million Earth life times to reach it (if I'm not underestimating).
Like if you don't know, then don't give me a bullshit answer like hypothesis, or estimation. Tell me what's tests have they done, or what proof that they have. Give me what these physicists did to say that the universe at time = t is size = x.[/QUOTE]
You aren't getting awnsers cause you are a dumb asshole
oh, dark matter... right, didn't see that there.
mirror effect. a light shoots off and bounces off clusters, thus, measuring the sources. etc etc.
google it if you're so damn curious. not exactly necessary to be an ass.
[QUOTE=BlackDeath292;20060219]oh, dark matter... right, didn't see that there.
mirror effect. a light shoots off and bounces off clusters, thus, measuring the sources. etc etc.
google it if you're so damn curious. not exactly necessary to be an ass.[/QUOTE]
Sorry, I felt like I was being trolled.
But the universe is supposedly 1.6*10^55 kg, how can one give this number?
My thought might not be right but send a radio wave out into space until it deflects off something and bounces back then measure half the time it took to get back. and you do this multiple times in different directions and so on.
Damn it ninja'd
Honestly, they have no fucking clue.
[QUOTE=TheMetalMan;20060245]Sorry, I felt like I was being trolled.
But the universe is supposedly 1.6*10^55 kg, how can one give this number?[/QUOTE]
Ask the scientists
Or use a goddamn search engine if you are that damn curious.
[QUOTE=Polaco202;20060246]My thought might not be right but send a radio wave out into space until it deflects off something and bounces back then measure half the time it took to get back. and you do this multiple times in different directions and so on.
Damn it ninja'd[/QUOTE]
no, actually, you're right. mirror effect.
how they got a number? don't know.
[QUOTE=Polaco202;20060246]My thought might not be right but send a radio wave out into space until it deflects off something and bounces back then measure half the time it took to get back. and you do this multiple times in different directions and so on.
Damn it ninja'd[/QUOTE]
Can you elaborate? Like what's the purpose of this? What is it bouncing off of? What's concluded from this regarding the mass/size of the universe?
[editline]04:14PM[/editline]
[QUOTE=OrDnAs;20060262]Ask the scientists
Or use a goddamn search engine if you are that damn curious.[/QUOTE]
I did, I couldn't get shit.
[QUOTE=TheMetalMan;20060266]Can you elaborate? Like what's the purpose of this? What is it bouncing off of? What's concluded from this regarding the mass/size of the universe?[/QUOTE]
bounces off of meteor clusters, planets, stars, etc. any matter in the universe. using dark matter as a strong support, the light reflects off measuring the distance.
you are aware that they depict the size of the universe from Earth's POV right?
Any values won't be massively accurate, but it can be estimated just by looking at the universe through telescopes.
Look at enough of the universe and you can figure out the density (number of galaxies within a certain volume.) We know the total volume of the the observable universe, so the number of galaxies within it can be calculated from the density.
The average galactic mass can be calculated using average solar mass * number of stars in a galaxy, or through observational methods such as gravitational lensing (the gravitational field of heavy objects can bend light that passes near it. The more the light is bent, the larger the mass.)
Apply this average galactic mass to the estimated total number of galaxies and you get the mass of the universe.
Basically you can't look at the whole universe and add up the mass of everything you can see, but you can investigate a small portion of the universe then extrapolate for the whole universe.
For example, you have a swimming pool full of sand. You want to know the weight of all this sand, but you cant put the swimming pool on a scale. But you can take out a bucket full of sand and put that on a weighing scale.
You know the volume of the swimming pool, and you now know the volume and mass of a bucket of sand. Apply what you know about the bucket of sand to the entire swimming pool and you have the mass of all the sand.
By the way, we [B]do[/B] know the volume of the observable universe. (The boundary is marked by the 'cosmic microwave background' which is an opaque after-glow of radiation from the big bang. There may be something outside this, but it's irrelevant for this question. If the observable universe is expanding faster than it can collapse, then it won't collapse, no matter what's outside it.)
[QUOTE=petieng;20060408]Any values won't be massively accurate, but it can be estimated just by looking at the universe through telescopes.
Look at enough of the universe and you can figure out the density (number of galaxies within a certain volume.) We know the total volume of the the observable universe, so the number of galaxies within it can be calculated from the density.
The average galactic mass can be calculated using average solar mass * number of stars in a galaxy, or through observational methods such as gravitational lensing (the gravitational field of heavy objects can bend light that passes near it. The more the light is bent, the larger the mass.)
Apply this average galactic mass to the estimated total number of galaxies and you get the mass of the universe.
Basically you can't look at the whole universe and add up the mass of everything you can see, but you can investigate a small portion of the universe then extrapolate for the whole universe.
For example, you have a swimming pool full of sand. You want to know the weight of all this sand, but you cant put the swimming pool on a scale. But you can take out a bucket full of sand and put that on a weighing scale.
You know the volume of the swimming pool, and you now know the volume and mass of a bucket of sand. Apply what you know about the bucket of sand to the entire swimming pool and you have the mass of all the sand.[/QUOTE]
Right, but if the universe is infinitely expanding, at an accelerated rate, there really isn't a fixed mass for it, yet I keep on hearing about a size or mass of the universe.
Also, how do physicists know that the universe is expanding?
[QUOTE=TheMetalMan;20060470]Right, but if the universe is infinitely expanding, at an accelerated rate, there really isn't a fixed mass for it, yet I keep on hearing about a size or mass of the universe.
Also, how do physicists know that the universe is expanding?[/QUOTE]
It isn't "infinitely expanding", the observable universe has a boundary, 13.7 billion light years away. There may be something past this boundary but it's impossible to reach it and it wouldn't matter anyway, if the observable universe is expanding faster than it can collapse, it will expand for ever.
Physicists know the universe is expanding from doppler shift measurements. As things move away, their light waves get 'stretched' and become more red. Like when an ambulance goes past you, and as it moves away the pitch of its siren gets lower.
[QUOTE=TheMetalMan;20060470]Right, but if the universe is infinitely expanding, at an accelerated rate, there really isn't a fixed mass for it, yet I keep on hearing about a size or mass of the universe.
Also, how do physicists know that the universe is expanding?[/QUOTE]
volume=/=mass
Probably the worst place to ask these questions, FP is full of teenagers.
[QUOTE=TheMetalMan;20060043]gtfo
[editline]03:58PM[/editline]
you too[/QUOTE]
lol ass-hat.
They extrapolaate the entire infinity of the Universe from a piece of fairy cake, into a small box, and put a person inside the box.
Cookie if you get the reference.
Very carefully.
They use a fuckton of mathematical calculations to do that
Sorry for making this thread, though it's very frustrating to just take some scientist's word for something like I'm it's religion or something. Thanks for trying guys.
OP, stop trying to be a smartass pls
I'm not. I'm just curious.
I'll explain the whole problem. You're trusting scientists. Don't believe what they say. They don't KNOW anything. Everything they say and do is based on theory and estimation. They don't know what they talking about.
they use math
[editline]12:22AM[/editline]
and science
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