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For example, for visible light, the refractive index of glass is typically around 1.5, meaning that light in glass travels at c / 1.5 ≈ 200 000 km/s (124 000 mi/s); the refractive index of air for visible light is about 1.0003, so the speed of light in air is about 90 km/s (56 mi/s) slower than c.
The constants listed here are known values of physical constants expressed in SI units; that is, physical quantities that are generally believed to be universal in nature and thus are independent of the unit system in which they are measured.
Faster-than-light (superluminal or supercausal) travel and communication are the conjectural propagation of matter or information faster than the speed of light in vacuum (c). The special theory of relativity implies that only particles with zero rest mass (i.e., photons ) may travel at the speed of light, and that nothing may travel faster.
6.7 × 10 −7 to 2.5 × 10 −5: 1 × 10 −15 to 3.7 × 10 −14: Calculated speed of an amoeba. [5] 10 −6: 1.52 × 10 −6: 5.4 × 10 −6: 3.4 × 10 −6: 5.1 × 10 −15: Speed of a cellular vesicle propelled by a motor protein. [6] 10 −5: 1.02 × 10 −5: 3.67 × 10 −5: 2.28 × 10 −5: 3.40 × 10 −14: Speed of the tip of a 7 cm ...
The h-cobordism theorem showed that (simply connected) manifolds of dimension at least 5 are much easier than those of dimension 3 or 4. The proof of the theorem depends on the " Whitney trick " of Hassler Whitney , which geometrically untangles homologically-untangled spheres of complementary dimension in a manifold of dimension >4.
The number π (/ p aɪ / ⓘ; spelled out as "pi") is a mathematical constant, approximately equal to 3.14159, that is the ratio of a circle's circumference to its diameter.It appears in many formulae across mathematics and physics, and some of these formulae are commonly used for defining π, to avoid relying on the definition of the length of a curve.
Therefore, the movements of the celestial bodies should be modified in the order v/c, where v is the relative speed between the bodies and c is the speed of gravity. The effect of a finite speed of gravity goes to zero as c goes to infinity, but not as 1/c 2 as it does in modern theories.
In SI units, the values of c, h, e and k B are exact and the values of ε 0 and G in SI units respectively have relative uncertainties of 1.6 × 10 −10 [16] and 2.2 × 10 −5. [17] Hence, the uncertainties in the SI values of the Planck units derive almost entirely from uncertainty in the SI value of G .