```ts
/**
 * The temperature in degrees Fahrenheit.
 */
export function celsiusToFahrenheit(celsius: number): number {
  const isValidNumber = typeof celsius === "number" && Number.isFinite(celsius);
  if (!isValidNumber) {
    throw new Error("celsius must be a finite number");
  }
  if (celsius < -273.15) {
    throw new Error("celsius must be at or above absolute zero");
  }
  return celsius * 1.8 + 32;
}

/**
 * The temperature in kelvin.
 */
export function celsiusToKelvin(celsius: number): number {
  const isValidNumber = typeof celsius === "number" && Number.isFinite(celsius);
  if (!isValidNumber) {
    throw new Error("celsius must be a finite number");
  }
  if (celsius < -273.15) {
    throw new Error("celsius must be at or above absolute zero");
  }
  return celsius + 273.15;
}

function validateCelsiusTemperature(celsius: number): void {
  const isValidNumber = typeof celsius === "number" && Number.isFinite(celsius);
  if (!isValidNumber) {
    throw new Error("celsius must be a finite number");
  }
  if (celsius < -273.15) {
    throw new Error("celsius must be at or above absolute zero");
  }
}
```