# Special relativity (mass-energy) Calculator

## Calculates the mass-energy of a body moving with some relative velocity with respect to the observer. | ||

- Purpose of use
- Rough estimate of a grain of sand impact at essentially the speed of light.

[1] 2022/07/19 07:04 50 years old level / A teacher / A researcher / Very /

- Purpose of use
- Independent check of a 250,000 kg mass impacting at .31C for a novel.

[2] 2022/03/16 23:42 60 years old level or over / Self-employed people / Useful /

- Purpose of use
- Determining the speed of the 1991 "Oh My God" particle event based on an assumption of it being a slightly less fast iron nucleus, and then applying that speed to a 4mg micrometeor (diameter of ~ 0.5mm) and calculating if the energy would be less or more than the energy of the Chicxulub impact event. 2,200,729,956,560,423,000 MJ seems to be roughly equivalent to 4 dinosaur-killing asteroid impacts at the same time.

[3] 2019/12/09 16:52 30 years old level / An office worker / A public employee / Useful /

- Purpose of use
- understanding why exceeding the speed of light would violate half of the known physics

[4] 2019/06/11 10:54 20 years old level / High-school/ University/ Grad student / Very /

- Purpose of use
- What would be the surface gravity of a DVD of the film 'Gravity' starting Sandra Bullock if it was accelerated to 99.99999999999702% the speed of light? The answer is a rather poultry 0.0000043g. This low number probably reflects the poor quality of the film.

[5] 2019/05/02 10:28 30 years old level / An office worker / A public employee / Very /

- Purpose of use
- To calculate the energy of an 866.67 fm³ mass of neutron degenerate matter at neutron star core density travelling at 99.9999% c.

[6] 2019/01/23 21:26 40 years old level / Others / Very /

- Purpose of use
- Determining yield of a liquid mercury-based RKV
- Comment/Request
- This is incredible.

[7] 2018/08/06 02:52 Under 20 years old / High-school/ University/ Grad student / Very /

- Purpose of use
- Sci-fi writing.
- Comment/Request
- Holy, this calculator is amazing. Thanks.

[8] 2018/02/04 23:51 20 years old level / An office worker / A public employee / Very /

- Purpose of use
- Had a silly little idea I rattling around in my head for years. Thought I could prove it wrong and put it to bed. Turns out it''s valid to more than 16 decimal points. Now I have to kind a competent physicist and ask him how WTF??? Thanks so much, if I had found this site earlier I would be finished now. ;-)

[9] 2018/01/31 08:34 60 years old level or over / A retired people / Very /

- Purpose of use
- Super useful for determining the power of a 2 cm diameter tungsten ball used in a Relative Kinetic Kill Vehicle.

[10] 2018/01/30 21:37 Under 20 years old / High-school/ University/ Grad student / Very /

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