Question 1

What fraction of light speed can spacecraft reach?

Accepted Answer

Current: ~0.00005c (New Horizons). Proposed solar sails: 0.2c. Physically possible: maybe 0.9c with future tech.

Question 2

How fast is light?

Accepted Answer

299,792 km/s in vacuum. Nothing with mass can reach light speed. At 0.9c, time dilation is significant.

Question 3

What's the fastest speed possible?

Accepted Answer

The speed of light (299,792,458 m/s or about 670 million mph) is the universal speed limit. Nothing with mass can reach it.

Question 4

Why do pilots and sailors use knots?

Accepted Answer

One knot = one nautical mile per hour. Nautical miles relate directly to Earth's latitude (1 nm = 1 minute of latitude), simplifying navigation.

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