What kind of civilization can life on Earth currently be classified as?
A) Type II
B) Type III
C) Type IV
D) Type I
D
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Many pulsars have periods that are gradually increasing as the spinning neutron stars lose energy
Indicate whether the statement is true or false
Superconductors have a primary advantage in that they will _______
a. reduce heating losses in transmission lines b. provide large magnetic fields for levitation c. be able to conduct more current d. allow electric motors to run almost forever
What do we mean by a runaway greenhouse effect?
A) a greenhouse effect that keeps getting stronger until all of a planet's greenhouse gases are in its atmosphere B) a greenhouse effect that starts on a planet but later disappears as gases are lost to space C) a greenhouse effect that heats a planet so much that its surface rock melts D) a process that heats a planet's surface, but that doesn't require the presence of greenhouse gases
Cubes of sugar, 1 cm on a side, are placed in water at 25ºC. Estimate the time before the lumps have dissolved; that is, when the sugar concentration at the lump is 10% by weight. Assume that the diffusivity of sugar into water is 6.9 x 10^-10m^2/s, the convective mass transfer coefficient is 6.4 x 10^-6m^2/s, and the self-diffusivity of sugar is 1 x 10^-5m^2/s. The density of sugar may be taken as 1500 kg/m^3.
What will be an ideal response?