HUBBLE OBSERVATIONS TEND TO SAY WHAT ABOUT HOW GALAXIES ARE MOVING?
The Universe as-we-know-it is theorized to brainstorm from the Large Blindside, the idea that the universe began small-scale and expanded. The Big Bang wasn't much of explosion, in fact it was the heating upward and spread of matter.
The first evidence of the Big Bang came from Edwin Hubble. His observations included estimating the distances of the galaxies course our ain. His observations on the light from the galaxies provided intriguing information. Hubble observed that absorption lines in the spectrum were nigh always "shifted" to longer wavelengths the redder surface area of the spectrum. Hubble chosen it "redshift."
The wavelengths tend to stretch as an object moves away from the observer. For case, a police car with information technology's sirens on will tend to change information technology's pitch as the car moves towards you and away from you. This is called Doppler shift.This is because the wavelengths of the sound changes every bit the waves come towards you and away. The waves coming towards you tends to be shorter in wavelength and the waves moving away from you have longer wavelengths.
Now, using galaxies, the Doppler shift works the aforementioned way. Galaxies (i.e The Andromeda Galaxy) coming towards us have wavelengths shorter than what they are originally supposed to be. Distant Galaxies on the other hand are moving abroad from u.s., causing their waves to be longer than originally measured. The wavelengths tend to stretch as an object moves away course the observer.
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| A galaxy coming towards us has a shorter wavelength than a galaxy receding. This is important for astronomers because information technology helps them understand how far away the galaxy is, and how fast it is receding/coming towards us. |
Hubble measured the amount of the shift in the spectra from the galaxies. He was able to calculate the recession velocities of the galaxies. This measurement is known equally Hubble's Law. Hubble's Law = The velocity at which a galaxy is moving away from us is proportional to the distance of that galaxy.
Hubble'due south Police: V= H x D
- V: The velocity of recession
- H: Hubble'due south constant
- D: altitude of milky way
In order to exist able to solve the law, data must be obtained. Hubble'due south constant is the result of comparison and observing the distance of many galaxies and compared the distances to the recession velocities of the galaxies. Hubble's constant is 22 km/due south/mly
The altitude of galaxies cannot be precisely measured, but astronomer have a good judge of how far away the galaxies are. They use many methods, such equally determining the parallax shift and the brightness of stars within galaxies. Parallax is the visual effect produced when nearby objects appear to shift position relative to more-distant objects. These indirect measurements of the altitude of galaxies often neglect when it is applied to distant galaxies. Distant Galaxies are observed past their intrinsic brightness, the amount of light actually emitted by the object.
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| A slap-up pic, showing what astronomers apply to find the distance of celestial objects such as stars and galaxies |
Nevertheless, a much more than accurate distance measurement can be made from the redshift of a milky way. This is called the Velocity-Distance relation, and it makes it possible to infer the distance of an object from a measurement of its spectrum. The amount of the shift varies directly with the bodily distance to the object. This is one of the reasons why redshift is and so important.
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| The definition of redshift |
After calculating the distance and Hubble's constant, a shut estimate of the velocity of the recession of the milky way can be made.
Hubble's law seems to imply that we are sitting at the center of the explosion, with everything moving abroad from u.s., just the expansion looks the aforementioned from any point in the universe. Hubble'due south law not only shows that the Universe is expanding, just we can too utilize the rate to determine how long this expansion has been occurring.
If we measure the distance betwixt two galaxies and then divide the distance by the velocity of recession, and then we can be able to make up one's mind how long it took for the the galaxies to reach their current altitude.
For case, a milky way 100 million light years (mly) abroad with a velocity of recession of ii,200 km/s would take 13.half-dozen billion years to reach it's current distance.
Because more afar galaxies also movement apart faster Hubble's police force says whatever ii galaxies achieve their present separation in the same 13.6 billion years. This means that the Universe is effectually 14 billion years old.
This was a generally easy summary, and I did not accept much questions on the expansion of the universe and redshift. I have washed a lot of groundwork reading on this topic earlier and this made sense to me. All the same I did have some questions. What is the Velocity-Distance Relation? The sources did not give much information nigh the verbal relation. Another question was that how do astronomers really determine the time galaxies take to accomplish their current altitude? I tried using the same format (100 mly / 2,200 km/due south) and I did not terminate upwards with 13.vi billion years. I ended up with something more like .045 mly/km/s. I don't know if I am doing the math correct, or if there is much more than advanced math needed.
Source: https://benschiher.blogspot.com/2014/03/redshift-and-its-relationship-to.html
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