RC

# In physics, redshift happens when light seen coming from an object is proportionally increased in wavelength, or shifted to the red end of the spectrum. The phenomenon is commonly seen in the spectra of astronomical objects. It can be seen in the spectra of stars, quasars, and galaxies. The observed redshift is proportional to the object's distance from the observer, and was first noticed in the 18th century by astronomer William Herschel. The most commonly accepted explanation of the redshift is that it is a Doppler shift that is proportional to the object's relative velocity with respect to the observer.

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##### Christina K.

Rutgers, The State University of New Jersey

##### Andy C.

University of Michigan - Ann Arbor

##### Marshall S.

University of Washington

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### Video Transcript

welcome to our second example video. Looking at relativistic energy in this video, we're going to consider a mass of 0.1 grams that is moving with a velocity equal to 0.9 the speed of light. And we'd like to find out what is its rest? Energy. What is its kinetic energy? And what is its total energy? Remember that rest energy will be EMC squared. Kinetic energy will be gamma minus one times EMC squared and total energy will be gamma EMC squared or alternatively, we can simply add he not decay gamma, in this case being one divided by the square root of one minus B squared or C squared or, in other words, one divided by the square root of one minus 10.9 squared. Hopefully, you can see here this point that gamma is always going to be greater than one. Unless V gets very, very small in cases, in which case it will be actually one, and we could end up with a zero kinetic energy. If it is small enough there now, looking at this, then we can plug in our numbers for Enoch, and we find that we have nine times 10 to the 12 jewels here for kinetic energy, we have 1.16 times 10 to the 13 jewels, and when we add these up to each other, we find that we have 2.6 times 10 to the 13 jewels, and so we can see the breakdown in the amount of energy of a macroscopic object of 0.1 g. Make sure here that you get it into kilograms and not just into grams. Now, looking at this, if we could take 0.1 g of material and turn it into energy, that's a lot of energy. And that's one of the things that scientists think about and in particular. The only way we have to do this right now is by stimulating radiate radiative properties, such as in nuclear power plants.

RC
University of North Carolina at Chapel Hill

#### Topics

Quantum Physics

Atomic Physics

Nuclear Physics

Condensed Matter Physics

##### Christina K.

Rutgers, The State University of New Jersey

##### Andy C.

University of Michigan - Ann Arbor

##### Marshall S.

University of Washington